1. Technical Field
The present invention relates generally to reducing degradation of surfaces, and more particularly to wear associated with localized damage of contact areas.
2. Background
Many surfaces are damaged by processes such as corrosion, deposition, film formation, growth of organisms, dissolution of passivating layers, and the like (hereinafter: damage processes). In some cases, damage may be caused by the process per se. In some cases, a product of the process (e.g., a particles of metal, oxide, a hydroxide, or salt) may cause damage (e.g., if the product of the process abrades or contaminates parts of the system). Some degradation processes (e.g., galvanic and/or crevice corrosion) may be localized, and may be associated with a contact area between different components. When damaged, this contact area may perform poorly.
Marine systems may be susceptible to degradation associated with seawater, particularly corrosion and biological processes (e.g., marine growth such as algae, barnacles, coral, and the like). Marine growth may degrade a surface, and products of marine growth may also degrade various components (e.g., abrasion from barnacles).
Mechanical systems often include a variety of components that interact via contact areas between components. An actuator may apply a force and/or displacement on various parts of the system, and may include such contact areas. Often, an actuator is coupled to a linkage, which may transmit force from the actuator to other parts of the system via contact areas. Other components, such as bearings, hinges, sensors, and the like, may include contact areas between components. A process that degrades a contact area between parts may significantly reduce the performance of a system based on those parts.
A hydraulic cylinder may comprise a piston that slides within a barrel. A fluid within the barrel applies pressure to the piston, sliding the piston in and out of the barrel. A hydraulic cylinder has a working length over which it operates, typically defined by a distance between one end of the barrel and an opposing, external end of the piston. An internal end of the piston moves within the barrel to vary length of the cylinder. If length is constrained at the endpoints, the cylinder may apply force between the endpoints, moving an object attached to one end of the cylinder with respect to an object attached to the piston at the other end. A piece of equipment requiring actuation from a hydraulic cylinder typically requires a specified range of motion, and this range of motion is used to determine the necessary working length of the cylinder chosen.
A seal between the barrel and piston of the cylinder allows the piston to slide while ostensibly preventing the passage of material (e.g., hydraulic fluid, dust, water, contaminants) from one side of the seal to the other. Some seals comprise materials that may corrode and/or induce corrosion. With a metallic seal contacting a piston of a dissimilar metal, galvanic corrosion between the seal and the piston may damage the contact area between the seal and the piston (e.g., corroding the seal or corroding the piston). A seal may create a localized chemical environment that, over time, may degrade the surface contacted by the seal.
A variety of apparatus use hydraulic cylinders that are exposed to degrading environments. Marine systems, such as steering systems, may use hydraulic cylinders in a variety of applications, which may include saline environments, extreme temperatures, and immersion in seawater for long times. Corrosion and/or surface growth of organisms may be problematic in marine environments, particularly at contact areas between parts, such as those areas disposed between components that slide past each other (e.g., a seal around a piston in a hydraulic cylinder). The reduction of such damage may improve the performance and/or lifetime of a product being used in a corrosive environment. This improvement may reduce the lifetime costs associated with a system, particularly a large system (e.g., a ship propulsion system) that may be remotely deployed and/or time consuming to repair.
U.S. Pat. No. 5,892,338 describes a radio frequency remote control for trolling motors. U.S. Pat. No. 5,246,392 describes a stern drive system with anti-rotation device. U.S. Pat. No. 5,720,635 describes a marine jet drive.